1. Field of the Invention
The invention relates to compositions and methods for repelling wild birds from target foods or places.
2. Description of the Prior Art
Several bird species cause monetary losses to agricultural production throughout the United States. For example, red-winged blackbirds (Agelaius phoeniceus), common grackles (Quiscalus quiscula), and brown-headed cowbirds (Molothrus ater) caused approximately US $13.4 million of damage to United States rice production in 2001 (Cummings et al. 2005, Economic impacts of blackbird damage to the rice industry. Wildlife Damage Management Conference. 11:317-322). Significant economic losses due to birds are also incurred in a number of other crops, including, but not limited to corn, fruit, grains, grasses, legumes, lettuce, millet, oats, rice, row crops, sorghum, sunflower, tree nuts, turf, vegetables, and wheat. Efforts to manage damages to rice and other crops have included the use of a variety of repellents and other nonlethal management alternatives (Werner et al. 2005, Evaluation of Bird Shield™ as a blackbird repellent in ripening rice and sunflower fields. Wildlife Society Bulletin. 33: 251-257). For example, chemical repellents can be used as seed treatments to reduce bird impacts to newly planted crops or as aerial applications to reduce bird consumption of ripening crops.
Methyl and dimethyl anthranilate (MA and DMA, respectively) are ester derivatives of anthranilic acid (also known as orthoamino-benzoic acid). MA, DMA and other derivatives of anthranilic acid as well as esters of phenylacetic acid, are known to be bird aversion agents with preferred embodiments as feed additives to deter feed loss (U.S. Pat. Nos. 2,967,128 and 4,790,990), and as an anti-grazing compound for geese and swans (Mason, J. R. et al., “Anthranilate Repellency to Starlings: Chemical Correlates and Sensory Perception”, JOURNAL OF WILDLIFE MANAGEMENT, 53:55-64 (1989)). Cinnamamide has also been shown to be a bird aversion agent (Crocker & Perry, PLANT CHEMISTRY AND BIRD REPELLENTS, 132: 300-308 (1990)).
U.S. Pat. No. 2,967,128 discloses the incorporation of MA and other ester derivatives of anthranilic acid as bird aversion agents into feed or pesticide additives, or into liquids to be sprayed on material. U.S. Pat. No. 4,790,990 teaches that the aversion agent can be at least partially trapped in a solid vehicle to improve its persistency. The solid vehicle can be a modified starch, oil or polymer which microencapsulates the aversion agent.
Schafer et al. (1983, The acute oral toxicity, repellency, and hazard potential of 998 chemicals to one or more species of wild and domestic birds. Archives of Environmental Contamination and Toxicology. 12:355-382) identified caffeine as a potential avian repellent with relatively low toxicity (LD50=316 mg/kg for European starlings [Sturnus vulgaris]). Avery and Cummings (2003, Chemical repellents for reducing crop damage by blackbirds. Pages 41-48 in Linz G. M. Proceedings of the management of North American blackbirds symposium. The Wildlife Society Ninth Annual Conference, 27 Sep. 2002, Bismarck, N. Dak., USA) found that 2,500 ppm caffeine reduced rice consumption by 76% among male red-winged blackbirds in captivity. Blackbirds consumed <10% of rice seeds treated with 10,000 ppm caffeine and >80% of untreated rice seeds under field conditions in southwestern Louisiana, USA (Avery et al. 2005, Caffeine for reducing bird damage to newly seeded rice. Crop Protection. 24: 651-657).
To extend the effectiveness of some repellents, repellent agents have been combined with visual cues or colors. These visual cues or colors serve as preingestive warnings to birds. Birds readily learn to associate these visual cues with unpleasant feeding experiences [Mason, Direct and observational avoidance learning by red-winged blackbirds (Agelaius phoeniceus): the importance of complex visual stimuli. In: T. Zentall and B. G. Galef, Editors, Social Learning: A Biopsychological Approach, Lawrence Erlbaum, Hillsdale, N.J. (1988), pp. 99-115].
While tastes are likely the most potent conditional stimuli in the process of mammalian food consumption [Garcia, Food for Tolman: cognition and cathexis in concert. In: T. Archer and L. Nilsson, Editors, Aversion, avoidance and anxiety, Erlbaum, Hillsdale (1989), pp. 45-85], food preference among bobwhite quail (Colinus virginianus) is affected by the color of food, and visual stimuli can actually overshadow salient tastes upon conditioning illness-induced aversions [Wilcoxon et al. 1971, Illness-induced aversions in rat and quail: relative salience of visual and gustatory cues, Science, 171:826-828]. Food aversions can be reliably conditioned in red-winged blackbirds (Agelaius phoeniceus) using toxic gavage (methiocarb and lithium chloride) paired with colored oats [Mason and Reidinger, 1983, Importance of color for methiocarb-induced food aversions in red-winged blackbirds, J Wildl Manage, 47:383-393]: oats colored differently from the color paired with LiCl were preferred through 4 weeks of post-treatment testing. Furthermore, conspecifics that observed aversive conditioning events similarly formed aversions to colors paired with toxicosis, even though they did not ingest the toxin themselves [Mason et al. 1984, Comparative assessment of food references and aversions acquired by blackbirds via observational learning, Auk, 101:796-803]. Similarly, quelea (Quelea quelea) [Elmandi et al. 1985, Calcium carbonate enhancement of methiocarb repellency for quelea, Trop Pest Manage, 31:67-72] and eared doves (Zenaida auriculata) [Rodriguez et al. An integrated strategy to decrease eared dove damage in sunflower crops. In: J. R. Mason, Editor, Repellents in wildlife management: proceedings of a symposium, National Wildlife Research Center, Fort Collins (1997), pp. 409-421] avoided calcium carbonate-treated crops when presence of the white powder was associated with methiocarb-induced toxicosis. Thus, at least for granivorous birds, color may be the dominant cognitive cue during the food consumption process and visual stimuli may enhance the efficacy of chemical repellents used to reduce bird damage to agricultural production [Avery and Mason, 1997, Feeding responses of red-winged blackbirds to multisensory repellents, Crop Prot, 16:159-164] and [Nelms and Avery, 1997, Reducing bird repellent application rates by the addition of sensory stimuli, Int J Pest Manage, 43:187-190].
However, despite these and other advances, the need remains for an improved system for repelling birds. Chemical repellent applications are typically constrained by a variety of factors, including cost, environmental effects, and food and feed safety. Thus, effective long-term repellence of birds from a target (i.e., food or place) typically requires repeated applications of the chemical repellents. However, repeated applications not only drive up costs, but such repeat applications may be limited to legally permissible aggregate concentrations of the repellent agent per season.